Heterogeneous networks comprise nodes of different transmit powers. Low power nodes (LPNs) do often have a smaller coverage area than macro nodes due to different power limitations. The coverage area of a cell can be defined as the area in which the node of the cell is best “heard” by a user equipment (UE) compared with neighbouring nodes, i.e. the cell provides the strongest downlink (DL) signal. LPNs are deployed for coverage in places where there is a particularly high load on the network (hot spots) or where the macro nodes have reduced coverage. LPNs can for instance be deployed indoors, covering a level/floor of a building or such. The deployment of an LPN within the coverage area of macro nodes results in transition zones where either downlink or uplink transmission may be sub-optimally transmitted. This is because within this transition zone, the path loss of a user equipment (UE) to the LPN is lower than the path loss to a macro node, e.g. because the UE is closer to the LPN than to the macro node. However, due to the reduced power of the LPN, the downlink (DL) power received by the UE in the transition zone is higher from the macro node than from the LPN.
The load on an LPN, e.g. at a hot spot, can vary much over time, why much of the capacity of the LPN may be unused. Cell range expansion can be used to expand the serving area of an LPN beyond its regular coverage area mentioned above, whereby the LPN can serve a UE even where the received DL power density is higher from the macro node than from the LPN. Power density is the power per frequency (power/Hz). However, the DL then experiences much interference from the macro node and the downlink received signal to interference and noise ration (SINR) at UEs associated to the LPN may be very low. Almost blank subframes (ABS) of the macro node can be used for reducing the DL interference, however then the utilization of the macro node resources is reduced.